Pump impeller molding apparatus

ABSTRACT

Apparatus for molding a plastic pump impeller having an annular coupling magnet totally enclosed and sealed within a hub formation traversed by a shaft bore. The plastic melt is injected into a special mold having movable core and magnet-supporting parts and means for actuating the same in a time sequence such that the melt forms the impeller configurations at one end of the magnet while the shaft bore is temporarily blocked off. The melt is caused to flow about the external aspects of the magnet toward the distal end thereof and then to resume the flow with timed opening up of the shaft bore to line the latter and complete the total envelopment of the magnet in unitary joinder with the impeller.

United States Patent Lalley PUMP IMPELLER MOLDING APPARATUS [72]Inventor: Donald P. Lalley, Elgin, Ill.

[73] Assignee: March Manufacturing Company,

Glenview, Ill.

[22] Filed: Dec. 23, 1969 [21] Appl. No.: 887,494

[52] [1.8. Cl. ..425/ 159, 425/249, 264/328 [51] Int. Cl. ..B29f 1/06[58] Field of Search .1 8/30 WM, 30 WC, 30 UM, 36,

18/5 E, DIG. 10, DIG. 38; 249/142, 144

[56] References Cited UNITED STATES PATENTS 3,543,349 12/1970 Marocco 18/30 WC 2,469,l30 5/1949 Rodman Jr. 18/30 WM 51 Oct. 24, 1972 PrimaryExaminer--R. Spencer Annear Attorney-Canard Livingston [57] ABSTRACTApparatus for molding a plastic pump impeller having an annular couplingmagnet totally enclosed and sealed within a hub formation traversed by ashaft bore. The plastic melt is injected into a special mold havingmovable core and magnet-supporting parts and means for actuating thesame in a time sequence such that the melt forms the impellerconfigurations at one end of the magnet while the shaft bore istemporarily blocked off. The melt is caused to flow about the externalaspects of the magnet toward the distal end thereof and then to resumethe flow with timed opening up of the shaft bore to line the latter andcomplete the total envelopment of the magnet in unitary joinder with theimpeller.

14 Claims, 6 Drawing Figures PATENTEDucI 241912 SHEEI 1 OF 3.INVEN'II'OR .D /7 hPLaZ/ y PATENTEDHIIT24 m2 3.700.372 sum 2 OF 3 f 4INVENTDRA Z3404 v PUMP IMPELLER MOLDING APPARATUS Various methods havebeen proposed forprotecting internal pump-coupling magnets fromcorrosive action of circulated chemically active liquids, and converselyprotecting the pumped liquids insensitive chemical and processingsystems against even minute contamination by the pump body, and magnetmaterials.

According to one commercial construction an impeller is formed of moldedplastic with shallow hub to which a separately encased coupling magnetis attached by cementing or suitable fusion of the material of theplastic envelope which encloses the magnet either partially or totallywith a lined shaft bore. Such methods do not readily admit of the use ofnewly developed plastic materials which are so. highly acid and alkaliproof at high temperatures that they are also immune to the solventactions needed to bond a separately encased magnet to a separatelyformed impeller body.

In accordancewith another construction an impeller is unitized with themagnet by conformation of the impeller configuration with hub portionsin which the magnet is simultaneously totally encased, inclusive of theshaft bore through the magnet. Such impellers have been especially madefor corrosive and chemically sensitive environments by hand casting withsubsequent machining ofthe cylindrical surfaces of the material whichencloses the magnet in order to procure a very thin plastic wall sectionat the peripheral boundary of the annular magnet so that maximummagnetic coupling efficiency can be achieved. I

In accordance with the present disclosures, a production method andapparatus is afforded which permits use of the highly chemicallyresistant plastic materials and produces a very thin and uniform plasticsection or skin-about the cylindrical aspects of the magnet, including arelatively thin section lining the shaft bore with no openings or leaks.l

Such a construction is achieved by use of the dis- .Closed mold meansincluding movable parts in the mold cavities which are actuated inaccordance with the methods and apparatus disclosed to cause the plasticmelt to follow a certain path in a one-shot injection in a .way to leavethe finished impeller free for automatic ejection when the mold opens.

More detailed aspects of novelty and utility characteristic of theinvention relate to the process, construction and operation of theapparatus and utilized in its practice set out in the followingdescription in view of the annexed drawings in which:

FIG. 1 is a vertical section through a centrifugal pumpof themagnetically coupled type utilizing a unitary plastic impeller andcoupling magnet of the type produced by the present disclosures;

FIG. 2 is an enlarged sectional detail of the impeller of FIG. 1;

FIG. 3 is a front view of the impeller with its cover plate removed,looking from left to right at FIG. 2;

FIG. 4 is a plan view of the cover plate for the impeller of FIG. 3;

modified to coact with the special mold means and processing apparatusdescribed.

FIG. 1 depicts a pump wherein the. pump body is formed entirelyofplastic material and comprises a housing section --A- and a separableclosure section -B-. secured to the housing by bolt means --C-.

The housing section includes an inlet port 10 opening into an impellerchamber 11 from which leads an outlet port 12. The closure section has aflange portion 13 fitting in sealed relation to the housing to close offthe impeller chamber, and a cylindrical well formation 14 extendsintegrally away from the chamber in coaxial alignment with the inletbore.

The impeller proper, generallyindicated at 15, is situated to rotate inthe impeller chamber and has a long hub portion 16 extending into thewell, a large, annular coupling magnetl7 being sealed within the hubformation so that its outer cylindrical periphery can rotate free of,but in closest possible proximity to the inner periphery of the well inorder to procure maximum magnetic couplingcoaction with an outer annulardriving magnet 18 seated in a carrier 19 rotated about the well by motormeans 20 i As seen inFIG. 3, the impeller configurations may take theform of approximately radially arcuate vanes 22 spaced about acentralshaft bore 23, and each vane v has on its upper edge spaced integralplastic studs 24 FIG. 5 is a fragmentary sectional view of moldingapparatus employed in the fabrication of the impeller unit and its coverplate;

FIG. 6 is a schematic illustrative of a process by which the impellerscan be molded in a one-shot operation in a known type of molding machineonly slightly Inn:

which fitinto holes 25 in a matching cover plate 26 such as shown inFIG. 4. This cover plate is manually fitted onto the vanes withthe studsin corresponding holes and the heads of the studs are heat pressed andflared, as at 27 in FIG. 2, to secure the cover plate in position, saidplate having a large central opening 28 to admit the pumped fluid fromthe port 10 in the assembly depicted in FIG. 1.

When the impeller comes from the mold it has no cover plate in position,and the vanes 22 will have the appearance seen in FIG. 3. However, theprocess admits of the simultaneous formation of a cover plate with eachimpeller, such cover plate being affixed in a later operation.

As seen in FIG. 2, the finished impeller has another added component inthe form of an insert sleeve bearing 30 formed largely of graphite andhaving an end flange 31 serving as a thrust bearing in the assembledcondition of the impeller with a fixed spindle 32, FIG. 1

The pump illustrated is of the larger type requiring a proportionatelylarge composite coupling magnet actually formed by cementing two annularmagnet rings 34 and 35 together along the line 37, it being notpresently commercially feasible to manufacture such large magnets as amonolithic body.

It is desirable in some instances to balance the impellers dynamically,and in the case of relatively large impellers of the type shown andweighing, for example, as much as 2 pounds, it becomes necessary toeliminate a large concentration of plastic in the region between theimpeller proper and the proximate end of the magnet in order to preventwarpage and stresses in the hub due to unequal cooling, and accordinglya metallic filler body 36, which may be an annulus of aluminum, forexample, is cemented to theaxial end of the magnet which will beproximate to the impeller itself. Before the impeller is completed byapplication of the insert bearing In FIG. 2 it will be observed that,apart from the in-:

serted graphite sleeve bearing 30, the bore through the annular magnetand filler bodies is fully lined with plastic material as at 33, so thatthe magnet and filler are totally shielded from any corrosive exposure,it being further observed that the shaft 32 in this type of pump isformed of inert ceramic material and will preferably be supported atboth axial ends, one in a bearing seat 40 formed in the end wall of themagnet well 14, and the other shaft end in an insert bearing 41 whichmay be of plastic or ceramic material in the corrosion proof pumps, andis fitted into a web across the inlet duct or port 10.

A process suitable for forming the described impeller (less the sleevebearing and an attached cover plate) may utilize a mold structure suchas depicted in FIG. 5, which comprises rightand left-hand separable moldsections or components I and II adapted to meet in closure along aparting line III in the known construction of injection molds.

Within mold section I is a large mold cavity 50 defining most of the hubconfiguration of the impeller and opening at the right-hand side intothe smaller cavity configurations 51 defining the head and impellerblades.

At the left-hand axial or distal end of the hub cavity is a mold wallportion 52 from which projects centrally and axially through the hubcavity into the impeller cavity, when the mold is closed, an elongatedcore and sleeve guide 53 over which telescopes a companionmagnet-supporting sleeve element 54 attached at its remote end to thepiston rod 55 of a hydraulic piston means 56 having inlet and outletcontrol-fluid ports 57 and 58.

When the mold is closed the free (left-hand) end of the hydraulicallydriven sleeve 54 will abut a shoulder 59 on the core and guide sleeveand complete, with the latter, a magnet-supporting rod structure ofuniform diameter fitting into the bore of the annular magnet and fillerbody assembly 34, 35, 36, which will be manually impaled upon the coreguide before the mold At the upper region of both mold sections and verya close to the parting line, are further mold cavity configurations v70defining a cover plate 26 for the impeller {of the type described inview of FIG. 4. The mold apparatus includes the usual knockout pins 71and 72,

respectively, for the impeller and cover plates, which serve to ejectthese pieces when the knockout bar 73 is closes, the complementarysupporting sleeve member 54 telescoping over the guide for the purposesaforesaid.

The left-handmold section I further includes a pin carrying member 60attached to a plunger 61 actuated by a lever 62 connecting at 63 to thepiston rod 64 of another hydraulic driving means 65 having inlet andoutlet ducts 66, 67 for the hydraulic operating fluid.

The pin carrying member 60 is provided with a plurality of registry pins68, of which there may be as many as eight arranged in a circleconcentric with the bore axis of the impeller (only one beingillustrated for clarity) and these pins are movable through the end wall52 of the hub cavity to engage the distal axial end of the magnet tospace the same slightly (for example, about 55' o'ne-thousandths of aninch) from the cavity wall so that the plastic melt can flow over thisend of the magnet. At a certain time in the operation of the process,these registry pins will be withdrawn so that the melt can fill into theresulting spaces and holes.

automatically actuated in the known manner ing of the mold.

on open- The described mold blocks 1 and II are adapted to seat in aknown type of molding machine caused to operate in accordance with themethods hereinafter described, and accordingly include the usualinternal channeling and connections for circulation of coolant withinthe blocks, which will also include an injection or sprue bushing 74surrounded by heating elements 75, together with an external injectionnozzle seat 76 adapted to receive the molding machine injection nozzle77.

The injected melt will pass from the injection duct 74A and fill intothe impeller and cover cavities, respectively, via runner passages 74Xand 74Z, it being observed that this melt will fill into the entireimpeller configuration first, and then work around the outer periphery69 of the inserted magnet assembly and thence around the distal axialend thereof, filling around the advanced registry pins 68 into the thinspace between the end of the magnet and the cavity wall 52 determined bythe slight projection of said pins.

At this juncture-in the process, the registry pins will be automaticallywithdrawn so that the melt can then complete coverage of the end of themagnet and work into the shaft bore, from which it will have beentheretofore substantially blocked owing to the presence of theretractable supporting sleeve element 54. Shortly following withdrawalof the registry pins-68, the supporting and filler sleeve means 54 willbe retracted by actuation of the hydraulic cylinder 56, the timing herebeing such, in conjunction with the temperature maintained in the moldblocks, that the very thin wall section of plastic surrounding themagnet periphery at 69 can harden sufficiently to support the magnetnotwithstanding withdrawal of the sleeve 54, the mold being opened uponconclusion of a curing cycle, determined by the usual machine clocks fora duration of about 1% minutes, with the sleeve fully withdrawn so thatejection of the completed impeller body and cover can be started in theknown manner by advance of the machine knockout pins 71, 72, before themold is fully open.

As will appear more fully from the following description of theoperation of the process, the registry pins and supporting sleeve willbe automatically reset to their respectively advanced positions as afunction of the conclusion of the molding cycle.

The schematic diagram of FIG. 6 depicts part of a form of conventionalmolding machine and its control equipment adapted to receive the moldmeans l-II of FIG. 5, together with a process control system working inconjunction with certain timed operations of such a machine toeffectuate the method of making the impeller, reference charactersheretofore introduced being repeated where appropriate, and it beingassumed that the two mold sections l and II, described in view of FIG.5, have been bedded in such machine in the known manner.

A molding cycle may be started after one of the mag- .net assemblies hasbeen placed by the attendant over the combination core and sleeve rod 53while the mold stands open, following which the attendant will shut theusual glass safety door 78 to initiate the machine cycle by closure ofthe usual door safety switch 80, thereby causing actuation of themachine injection control means 81 to operate the closing ram 82 andmove the mold section 1 into closure with the companion section II,which in turn will cause closure of the usual forward limit switch means83 to actuate a master machine relay means 84 permitting the melt to beinjected through the machine nozzle 77.

As previously mentioned, the registry pins 68 and the magnet supportingsleeve 54 are respectively standing in advanced condition before themold closes, and when the forward limit switch 83 is actuated by closureof the mold to pull in the master relay 84, the latter also operates areset relay means 85 forming part of the process control system and thereset relay causes a holding relay means 86 to operate and lock itselfin.

Reset relay 85 starts a timing means including two conventional clockswitches 87 (T-l) and 88 (T-2), the timing of T-l being such as to allowan interval in which the melt can work entirely into the space about thedistal end of the magnet determined by the advanced condition of theregistry pins 68; and at the conclusion of this interval, timer T-l willstart the hydraulic pump means P-l to activate piston means 65, andcause retraction of the registry pins 68 so that the melt can fill theholes left thereby. A pressure limit switch 90 will automatically stoppump P-l when the pins are fully withdrawn.

A few tenths of a second following withdrawal of the registry pins,clock switch T-2 will start the second hydraulic control pump means P-2and activate the sleeve hydraulic piston means 56 to retract the magnetsupporting sleeve 54, this pump being automatically stopped by anotherpressure limit switch means 91.

At the time the registry pins are withdrawn, as aforesaid, the plasticskin or sheath about the outer cylindrical periphery of the magnetassembly will be sufiiciently hard, owing to the very thin sectionthereof and the maintained temperature of the mold, to support themagnet while the sleeve means 54 retracts its support, and about thetime the pressure limit switch means 91 for pump P-Z stops this pump,the usual machine clock system will, in known manner, have .completedthe curing and cooling phase of the conventional machine cycle (asdistinguished from the process cycle)'and cause the ram thereby toreverse and open the mold, the forward injection switch 83 therebydropping out the Master Machine Relay 84 and the Reset Relay 85 andcausing timer T-l to reset automatically and close normal contacts whichwill start pump P-l again in reverse, so that the registry pins are onceagain advanced into the mold cavity as a function of the opening of themold, this pump P-l being stopped again by another pressure limit switchmeans 90X.

Movement of the mold into fully open position causes operation of aspecial Process Reset Switch'92, provided for control of the process,and actuated by the mold on full opening thereof, to drop out the holdrelay means 86 and thereby reset the second timer T-2, which in turnwill reverse (through normal contacts,

part thereof) the second pump P-2 causing the magnet supporting sleeveto be restored to advanced position, this pump being automaticallystopped by its pressure limit switch means 91X, thereby terminating theprocess cycle with the mold standing open in readiness for applicationof another magnet assembly and initiation of a new molding cycle, themolded impeller and its cover plate being automatically ejected into asuitable receptacle in known manner by action of the knockout pins 71,72 attendant upon the terminal operations of the machine, beginning withthe opening of the mold.

Thus the process provides for actuation of certain movable moldcomponents in a certain timed coaction with the basic machine moldingcycle to effect the steps of a method in which the melt is flowedprogressively or in stages to form certain initial configurations, andthe melt is then caused to flow outwardly over external aspects of theconjoined magnet and subsequently into and through internal aspectsthereof defining the shaft bore, in timed dependence upon the timedmovements of the movable mold elements and pre-hardening of thin-walledsections of the envelope about the magnet.

The time cycle of the illustrative arrangement and operation issubstantially the cycle of the molding machine from the time the safetydoor is closed to initiate the cycle until the mold again stands open. Atypical cycle may be of 2 minutes or 120 seconds duration, in which thefirst second is utilized for the fill, which is very rapid under thehigh pressures usually employed in such machines, and of this 1 second,about 0.4 second is used to retract the registry pins and normally 0.6second for retracting the sleeve, although different runs may extendthis latter interval to as much as 0.8 to 1 second. As much as secondsmay be allotted to curing and cooling, and 3 seconds allowed forejection of the object by the knockout pins, with a final 6 seconds forhydraulic resetting of the registry pins and sleeve.

The process may employ either thermoplastic or therrnosetting materials,a very satisfactory material for fabrication of the described pumpimpellers being a thermoplastic of the class of polypropylenesuch, forexample, as the proprietary material known as Penton (Hercules PowderCo.).

In general, the apparatus and method are not limited to the fabricationof pump impellers, but may be employed for production molding of avariety of other items required to have totally included therein someother object having a melting point unaffected by the temperature andpressure conditions required for the principal item or form, where theincluded object has a perforation, bore, or other configurationcompatible with support thereof by the compound core means disclosed;and accordingly no limitations are intended or implied in the foregoingillustrative description except as may attend the appended claims.

Iclaim:

1. Mold means adapted to receive an injected plastic melt for forming asa unitary body a pump impeller having a through bore for a shaft,together with an annular magnet totally sealed therein concentricallywith said bore, said mold means comprising a mold structure includingseparable mold sections having respective cavity configurations definingsaid body in the closed condition thereof; compound core means for theshaft bore comprising elongated and respectively fixed and movable coremembers the movable one of which is adapted to telescope with the fixedmember in said closed condition, the fixed core member projecting from aparticular wall portion of the cavity configurations in one of saidsections, and the movable core member being carried at one supported endthereof in the other section by movable means operative to advance andretract such core member axially into and from telescoped interfit withthe fixed member, said core members being spaced apart in the separatedopen condition of the mold sections to admit placement of a magnetannulus upon the fixed member, said movable core member in the advancedcondition thereof being moved into interfit with the fixed'member byclosure of the mold sections to complete a core structure defining saidshaft bore and blocking off entry of the melt therein; the supportedmagnet having an axial end proximate to the impeller configurations ofsaid body and a distal end remote therefrom and confronting saidparticular wall portion of the mold cavity, said particular wall portioncommunicating with adjoining cavity portions surrounding the outercylindrical aspect of the magnet such that the melt can progress fromsaid aspect to fill over said distal end; duct means for admitting andguiding injected plastic melt into the mold structure in a generaldirection to fill into the impeller configurations at the proximate endof the magnet and progress over said cylindrical aspect and thence oversaid distal end thereof with a tendency to move finally into the borefrom which it is blocked, however, by the presence of the interfittedmovable core member until the latter is withdrawn; registry meansincluding at least one registry member movable for advance into andretraction from a registry position between said particular mold wallportion and the distant end of the magnet to space the latter forfilling of the melt thereover as aforesaid; and actuating means operableto move said movable core member and said registry means independentlyto and from the respective advanced and retracted positions thereof.

2. Apparatus according to claim 1 wherein the advanced position of saidregistry member and direction of progress of the melt is such as to havea tendency to force the magnet and the distal end thereof in an axialdirection against said member whereby to afford a uniform cavity spacethereat and consequent uniform wall thickness of the plastic over saiddistal end of the magnet.

3. Apparatus according to claim 1 further characterized in that thereare a plurality of said registry members arranged about the axial centerof the shaft bore at said distal end of the magnet and said members arejointly movable by the appertaining actuating means in approximateparallelism with the axis of the shaft bore in moving into and from saidadvanced and retracted registry position thereof.

4. Apparatus according to claim 1 wherein said elongated fixed coremember is mounted at one end upon said particular wall portionconcentrically with the center of the axis of the shaft bore and saidregistry .member is a pin reciprocable in said particular wall portionat a location disposed radially of said center for movement asaforesaid.

5. Apparatus according to claim 1 wherein said actuating means comprisesseparate reversible hydraulic piston devices respectively having drivingconnection with one of said registry members and movable core membersand respectively operative to move the same in the manner and for thepurposes aforesaid.

6. Apparatus according to claim 5 wherein the hydraulic piston devicesrespectively driving the re gistry means and movable core member arecontained within the appertaining mold sections.

7. Mold means in accordance with claim 1 wherein said mold sections meetalong a parting line which intercepts the cavity configurations definingthe impeller configurations of said body, and said melt-admitting andguiding duct meanshas an injection entry in the mold section having themovable core member communication through duct passages along saidparting line into said impeller defining cavity configurations, suchthat in the closed condition of the sections the melt first enters saidlast-mentioned configurations to fill the same and then progressestherefrom over the cylindrical aspects to the distal end of the magnetsupported on the core means as aforesaid.

8. Molding apparatus for forming a principal plastic object by injectionof a melt into a mold cavity, said object having totally includedtherein a second and previously formed object of a character which willnot be materially affected by the temperature required for the melt,said apparatus comprising relatively separable mold memberscooperatively defining a cavity formation for the configuration of theprincipal object in closed condition of the mold members; and anelongated compound core structure comprising relatively fixed andmovable elongated core members, one of which is fixed at one end in oneof said mold members and projects axially into a part of said cavityformation, and the other of which is carried by the remaining moldmember in axial alignment with the fixed core member, one said coremember telescoping with the other; drive means operatively associatedwith the mold member having the movable core member and operative tomove said movable core member into and withdraw it from telescopedrelation with the fixed core member in the closedcondition of said moldmembers, at least; said movable core member being adapted to supportsaid second object in withdrawn condition and carry the same with it intelescoping with the fixed core member to dispose the second object in apredetermined position in said cavity formation in the closed conditionof the mold members; and means for guiding melt in said closed moldmembers into said cavity formation along a predetermined path to formthe principal object and partly envelope the second object while thecore members are in telescoped relation, and thereafter permitcompletion of the flow of the melt responsive to withdrawal of themovable core member from telescoped relation with the fixed member byactuation of said drive means while the mold members are still in closedcondition, whereby to complete the principal object with totalenvelopment thereby of the second object.

9. Apparatus according to claim 8 further characterized in that saiddrive means is hydraulically actuated and contained within that one ofthe mold members which has the movable core member.

10. Apparatus according to claim 8 further characterized in that amovable registry member is included as apart of the particular moldmember having the fixed core member, together with second drive meansoperatively associated with said particular mold member and operative tomove said registry member to and from engagement with said second objectin the telescoped relation of said core members to space said secondobject a predetermined distance from a part of said cavity formation andthereby determine a portion of said predetermined flow path.

11. Apparatus according to claim 10 wherein the respective drive meanscomprises reversible hydraulically driven piston means having connectionwith said movable core member and registry member for respectivelyactuating the same in the manner and for the purposes set forth.

12. In a mold for forming a principal object from a plastic meltinjected therein under pressure and having a secondary object whollycontained therein, separable mold members defining a forming cavity forthe principal object in their closed relation; a first elongated coremember affixed at one end to one of said mold members and projectingwith a free end into said cavity; a second core member having one endmounted in the other said mold member and a tubular portion extending toa free end thereof and movable axially onto and from closing telescopedengagement with the first core member over the free end thereof to blockflow about said first core member, said movable core member beingadapted to support said secondary object by placement of the latterthereon in the open condition of said mold members, said supportedsecondary object being disposed in a predetermined position in saidcavity in closing telescoped relationship of the movable core member asaforesaid in the closed condition of the mold members; and means in oneof said mold members, at least, directing injected plastic melt along apredetermined flow path into said cavity to form said principal objectand cover outer portions of the supported secondary object not blockedby said telescoped core members; and reversely operable actuating meanscooperable with the supporting means for the movable core member andoperative to move the latter to and from telescoped relation with thefixed core member such that said melt can fiow about the fixed coremember responsive to withdrawal of the movable core member from closingtelescoped engagement as aforesaid to complete the formation of theprincipal object with total envelopment of the secondary object.

13. Apparatus for molding a plastic pump impeller having a shaft boreand an annular coupling magnet sealed within its confines inconcentricity with said bore, which comprises supporting means for themagnet including a core means in the cavity of a mold having a fixedelongated core rod and a coaxially movable core rod with hollow portionstelescoping onto the fixed rod, said magnet being supported upon thehollow one of said rods in the separated condition thereof, meansoperative to bring said rods into telescoped relationship to affordsupport along the bore of the magnet annulus and to define a shaft borefor the impeller; means guiding flow of injected plastic melt into saidc avit in a raegion thereof defining im ller configuratrons ocate at aproximate axial end 0 the magnet to flow progressively along the outercylindrical aspects thereof and onto the opposite distal end of themagnet; means spacing said distal end of the magnet temporarily from awall of the cavity to permit the melt to cover said distal end, meansoperative in timed relation to said melt flow to withdraw the movablecore member from telescoped engagement with the fixed core member topermit further flow of the melt into the shaft bore about the fixed coremember as the movable core member retreats whereby -to line said boreand complete the total envelopment of the magnet as a wholly containedpart of the impeller.

14. Apparatus for molding a plastic pump impeller of the type comprisinga body having impeller configurations situated at one axial end of a hubconfiguration and an annular coupling magnet totally contained andsealed within said hub configuration and a shaft bore extending througha distal axial end of the hub configuration and the magnet annulus andthrough the opposite axial end of the magnet annulus which is proximateto the impeller configurations and which opens through the latterconfigurations, said apparatus comprising an elongated core member inthe impeller-forming molding cavity formed by complementary separableand closable mold sections, the core member comprising separable coaxialrelatively telescoping portions concentric with the required shaft boreand axially separable by movement of the movable one of the core membersand also by opening movement of the appertaining mold section onseparation from the companion section, means guiding injected plasticmelt along a predetermined path within said mold sections in closedcondition, said path leading first into impeller forming configurationsof said cavity and thence about the outer cylindrical aspects of themagnet annulus to the distal end thereof; means spacing said distal endof the magnet from a wall portion of the cavity to form a plasticcoating over said distal end; and means operative to separate themovable core member from the fixed core member to admit movement of themelt for full flow about the fixed core member thereby coating the innerthe magnet annulus and defining a fully plastic lined shaft bore passagethrough the entire impeller.

UNITED swi'ss ?A'IE'NT ewes CERTIFICATE 6F CGBREC'I'ION Patent No,3,700,372 Dated October 2a, 1972 Donald P, Leliey 1-2; is certified thaterrer appears in the above- Mentified Letters Patent and that saidLetters Petewt are hereby corrected as shown below:

(301mm 10 line 53 (Claim 111), after "inner", insert Me-periphery of,

Signed and sealed this 29th day of May 1973.

(SEAL) Attes't:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer v vCommissioner of Patents

1. Mold means adapted to receive an injected plastic melt for forming asa unitary body a pump impeller having a through bore for a shaft,together with an annular magnet totally sealed therein concentricallywith said bore, said mold means comprising a mold structure includingseparable mold sections having respective cavity configurations definingsaid body in the closed condition thereof; compound core means for theshaft bore comprising elongated and respectively fixed and movable coremembers the movable one of which is adapted to telescope with the fixedmember in said closed condition, the fixed core member projecting from aparticular wall portion of the cavity configurations in one of saidsections, and the movable core member being carried at one supported endthereof in the other section by movable means operative to advance andretract such core member axially into and from telescoped interfit withthe fixed member, said core members being spaced apart in the separatedopen condition of the mold sections to admit placement of a magnetannulus upon the fixed member, said movable core member in the advancedcondition thereof being moved into interfit with the fixed member byclosure of the mold sections to complete a core structure defining saidshaft bore and blocking off entry of the melt therein; the supportedmagnet having an axial end proximate to the impeller configurations ofsaid body and a distal end remote therefrom and confronting saidparticular wall portion of the mold cavity, said particular wall portioncommunicating with adjoining cavity portions surrounding the outercylindrical aspect of the magnet such that the melt can progress fromsaid aspect to fill over said distal end; duct means for admitting andguiding injected plastic melt into the mold structure in a generaldirection to fill into the impeller configurations at the proximate endof the magnet and progress over said cylindrical aspect and thence oversaid distal end thereof with a tendency to move finally into the borefrom which it is blocked, however, by the presence of the interfittedmovable core member until the latter is withdrawn; registry meansincluding at least one registry member movable for advance into andretraction from a registry position between said particular mold wallportion and the distant end of the magnet to space the latter forfilling of the melt thereover as aforesaid; and actuating means operableto move said movable core member and said registry means independentlyto and from the respective advanced and retracted positions thereof. 2.Apparatus according to claim 1 wherein the advanced position of saidregistry member and direction of progress of the melt is such as to havea tendency to force the magnet and the distal end thereof in an axialdirection against said member whereby to afford a uniform cavity spacethereat and consequent uniform wall thickness of the plastic over saiddistal end of the magnet.
 3. Apparatus according to claim 1 furthercharacterized in that there are a plurality of said registry membersarranged about the axial center of the shaft bore at said distal end ofthe magnet and said members are jointly movable by the appertainingactuating means in approximate parallelism with the axis of the shaftbore in moving into and from said advanced and retracted registryposition thereof.
 4. Apparatus according to claim 1 wherein saidelongated fixed core member is mounted at one end upon said particularwall portion concentrically with the center of the axis of the shaftbore and said registry member is a pin reciprocable in said particularwall portion at a location disposed radially of said center for movementas aforesaid.
 5. Apparatus according to claim 1 wherein said actuatingmeans comprises separate reversible hydraulic piston devicesrespectively having driving connection with one of said registry membersand movable core members and respectively operative to move the same inthe manner and for the purposes aforesaid.
 6. Apparatus according toclaim 5 wherein the hydraulic piston devices respectively driving theregistry means and movable core member are contained within theappertaining mold sections.
 7. Mold means in accordance with claim 1wherein said mold sections meet along a parting line which interceptsthe cavity configurations defining the impeller configurations of saidbody, and said melt-admitting and guiding duct means has an injectionentry in the mold section having the movable core member communicationthrough duct passages along said parting line into said impellerdefining cavity configurations, such that in the closed condition of thesections the melt first enters said last-mentioned configurations tofill the same and then progresses therefrom over the cylindrical aspectsto the distal end of the magnet supported on the core means asaforesaid.
 8. Molding apparatus for forming a principal plastic objectby injection of a melt into a mold cavity, said object having totallyincluded therein a second and previously formed object of a characterwhich will not be materially affected by the temperature required forthe melt, said apparatus comprising relatively separable mold memberscooperatively defining a cavity formation for the configuration of theprincipal object in closed condition of the mold members; and anelongated compound core structure comprising relatively fixed andmovable elongated core members, one of which is fixed at one end in oneof said mold members and projects axially into a part of said cavityformation, and the other of which is carried by the remaining moldmember in axial alignment with the fixed core member, one said coremember telescoping with the other; drive means operatively associatedwith the mold member having the movable core member and operative tomove said movable core member into and withdraw it from telescopedrelation with the fixed core member in the closed condition of said moldmembers, at least; said movable core member being adapted to supportsaid second object in withdrawn condition and carry the same with it intelescoping with the fixed core member to dispose the second object in apredetermined position in said cavity formation in the closed conditionof the mold members; and means for guiding melt in said closed moldmembers into said cavity formation along a predetermined path to formthe principal object and partly envelope the second object while thecore members are in telescoped relation, and thereafter permitcompletion of the flow of the melt responsive to withdrawal of themovable core member from telescoped relation with the fixed member byactuation of said drive means while the mold members are still in closedcondition, whereby to complete the principal object with totalenvelopment thereby of the second object.
 9. Apparatus according toclaim 8 further characterized in that said drive means is hydraulicallyactuated and contained within that one of the mold members which has themovable core member.
 10. Apparatus according to claim 8 furthercharacterized in that a movable registry member is included as a part ofthe particular mold member having the fixed core member, together withsecond drive means operativelY associated with said particular moldmember and operative to move said registry member to and from engagementwith said second object in the telescoped relation of said core membersto space said second object a predetermined distance from a part of saidcavity formation and thereby determine a portion of said predeterminedflow path.
 11. Apparatus according to claim 10 wherein the respectivedrive means comprises reversible hydraulically driven piston meanshaving connection with said movable core member and registry member forrespectively actuating the same in the manner and for the purposes setforth.
 12. In a mold for forming a principal object from a plastic meltinjected therein under pressure and having a secondary object whollycontained therein, separable mold members defining a forming cavity forthe principal object in their closed relation; a first elongated coremember affixed at one end to one of said mold members and projectingwith a free end into said cavity; a second core member having one endmounted in the other said mold member and a tubular portion extending toa free end thereof and movable axially onto and from closing telescopedengagement with the first core member over the free end thereof to blockflow about said first core member, said movable core member beingadapted to support said secondary object by placement of the latterthereon in the open condition of said mold members, said supportedsecondary object being disposed in a predetermined position in saidcavity in closing telescoped relationship of the movable core member asaforesaid in the closed condition of the mold members; and means in oneof said mold members, at least, directing injected plastic melt along apredetermined flow path into said cavity to form said principal objectand cover outer portions of the supported secondary object not blockedby said telescoped core members; and reversely operable actuating meanscooperable with the supporting means for the movable core member andoperative to move the latter to and from telescoped relation with thefixed core member such that said melt can flow about the fixed coremember responsive to withdrawal of the movable core member from closingtelescoped engagement as aforesaid to complete the formation of theprincipal object with total envelopment of the secondary object. 13.Apparatus for molding a plastic pump impeller having a shaft bore and anannular coupling magnet sealed within its confines in concentricity withsaid bore, which comprises supporting means for the magnet including acore means in the cavity of a mold having a fixed elongated core rod anda coaxially movable core rod with hollow portions telescoping onto thefixed rod, said magnet being supported upon the hollow one of said rodsin the separated condition thereof, means operative to bring said rodsinto telescoped relationship to afford support along the bore of themagnet annulus and to define a shaft bore for the impeller; meansguiding flow of injected plastic melt into said cavity in a regionthereof defining impeller configurations located at a proximate axialend of the magnet to flow progressively along the outer cylindricalaspects thereof and onto the opposite distal end of the magnet; meansspacing said distal end of the magnet temporarily from a wall of thecavity to permit the melt to cover said distal end, means operative intimed relation to said melt flow to withdraw the movable core memberfrom telescoped engagement with the fixed core member to permit furtherflow of the melt into the shaft bore about the fixed core member as themovable core member retreats whereby to line said bore and complete thetotal envelopment of the magnet as a wholly contained part of theimpeller.
 14. Apparatus for molding a plastic pump impeller of the typecomprising a body having impeller configurations situated at one axialend of a hub configuration and an annular coupling magnet totallycontained and sealed within said hub configuration and a shaFt boreextending through a distal axial end of the hub configuration and themagnet annulus and through the opposite axial end of the magnet annuluswhich is proximate to the impeller configurations and which opensthrough the latter configurations, said apparatus comprising anelongated core member in the impeller-forming molding cavity formed bycomplementary separable and closable mold sections, the core membercomprising separable coaxial relatively telescoping portions concentricwith the required shaft bore and axially separable by movement of themovable one of the core members and also by opening movement of theappertaining mold section on separation from the companion section,means guiding injected plastic melt along a predetermined path withinsaid mold sections in closed condition, said path leading first intoimpeller forming configurations of said cavity and thence about theouter cylindrical aspects of the magnet annulus to the distal endthereof; means spacing said distal end of the magnet from a wall portionof the cavity to form a plastic coating over said distal end; and meansoperative to separate the movable core member from the fixed core memberto admit movement of the melt for full flow about the fixed core memberthereby coating the inner the magnet annulus and defining a fullyplastic lined shaft bore passage through the entire impeller.